1. Field of the Invention
The present invention relates to a method of and mechanism for indicating the speed of fishing gear trolled by a fishing boat relative to surrounding water at the trolling depth.
2. Prior Art
It is known that the fish-attracting effectiveness of bait, either natural bait or artificial lures, trolled through water varies greatly with the "trolling speed", that is, the speed of the bait relative to surrounding water at the trolling depth. If the bait is trolled too fast or too slow, the "action" of the bait is incorrect for optimum attraction of fish. The optimum range of trolling speeds varies with the bait being used and also with the species of fish to be attracted. For some species, such as Chinook salmon, few fish are attracted if the trolling speed is outside of a very narrow range.
Up to now, determination of the actual trolling speed at the trolling depth has been largely a matter of guesswork. Some fishermen rely entirely on the speeds of their fishing boats relative to surface water in their attempts to set the actual trolling speed at an optimum rate. Others attempt to gauge trolling speed by the angles of their weighted fishing lines, or the tag lines to which their fishing lines are attached, relative to their fishing boats, taking into consideration the amount of weight being used to maintain the bait at a desired depth. Others merely vary boat speed until a fish is caught and then either try to maintain about the same boat speed or continue varying boat speed.
Experienced fishermen recognize that actual trolling speed is affected by surface currents, subsurface currents, tidal action, wave action and wind, and that, consequently, boat speed or fishing line angle are poor indicators of actual trolling speed. Such experienced fisherman usually try to maintain about the same boat speed or fishing line angle that previously has produced good results in the same location under similar conditions, or totally ignore boat speed and fishing line angle and instead rely on their "feel" of the action of the bait or lures.
Maintaining correct trolling speed is particularly important when bait is trolled deep and/or slowly. For example, for Chinook salmon fishing bait is trolled at various depths up to 90 fathoms and the difference between water speed on the surface and at any depth below even 5 or 10 fathoms often is large. In addition, some lures for Chinook salmon fishing are designed to be trolled between a minimum and maximum speed separated by about 0.3 or 0.5 knot, usually within the range of 1.5 knots to 4.0 knots. Such accuracy is impossible to maintain at such slow trolling speeds if the skipper does not know the actual water conditions at the trolling depth.